The invention relates generally to the field of nuclear medicine and, more specifically, to diagnostic techniques of analyzing blood flow through the heart by detecting radioactivity from radioisotopes injected into the bloodstream.
In addition to the standard tools of cardiac diagnosis, the electrocardiogram (ECG) and the conventional stethoscope for audible heart sounds, relatively new techniques including angiograms, ultrasound cardiography and the measurement of radioactivity in the blood are being investigated and implemented to increase the amount of quantitative data to provide a more reliable basis for diagnosis. In ascertaining the efficiency of the heart, it is desirable to determine the volumetric rate of flow of blood through the heart. For example, the difference in volume of the left ventricle during different phases of the cardiac cycle is indicative of the rate of blood flow.
Volumetric measurements can be approximated by using X-ray or ultrasound imaging techniques. Another type of X-ray technique is shown in U.S. Pat. No. 3,824,399 to Bjork et al which indicates the concentration of an X-ray opaque tracer in the heart over a period of several cardiac cycles to generate quantitative data concerning the rate of blood flow. The same type of technique was earlier employed by injecting a radioisotope into the blood stream entering the heart and using a scintillation detector or Geiger counter to determine the variations in concentration of the radioactive tracer in the outflow tract of the heart over several cardiac cycles. The collected data was plotted and used to determine the rate of blood flow through the heart. See, for example, U.S. Pat. Nos. 3,221,731 and 3,528,407 to Vigoulet et al.